Network Virtualization over Layer 3 (NVO3) is a technology for implementing network virtualization. By means of this technology, a physical network can be virtualized, so that the network can be used by different tenants together. An NVO3 encapsulation header includes a 24-bit virtual network identifier (VN ID). Different VN IDs are used to identify different virtual networks (Virtual Network, VN), and different VN IDs may be used to isolate traffic between different tenants belonging to different VNs.
Typical data encapsulation in the NVO3 technology includes a Virtual Extensible Local Area Network (VXLAN), Network virtualization Generic Routing Encapsulation (NVGRE), and the like. The VXLAN uses an encapsulation manner of Media Access Control (MAC) In User Datagram Protocol (UDP), and the NVGRE uses an encapsulation manner of MAC In Generic Routing Encapsulation (GRE).
An edge device of an NVO3 network is referred to as a network virtualization edge (NVE). The NVE accesses a tenant end system (TES), and the TES may be briefly referred to as a tenant system (TS). The NVE is similar to a Provider Edge (PE) device in a Border Gateway Protocol (BGP)/multiprotocol label switching (MPLS) Internet protocol (IP) virtual private network (VPN) network, and the TS is similar to a Customer Edge (CE) device in a BGP/MPLS IP VPN network. The NVE may be located on a server or a physical network device, and the TS may be a value-added service device such as a virtual machine of a server, a physical server, a firewall, or a load balancer.
The NVO3 network is increasingly widely applied to a data center (DC).
An MPLS VPN network is widely deployed in a conventional telecommunications network. The MPLS VPN includes a layer 2 (L2) VPN and a layer 3 (L3) VPN. A user needs to access a data center by using an MPLS VPN network, and the MPLS VPN network and the NVO3 network generally belong to two autonomous system (AS) domains, when the data center is accessed by using the MPLS VPN network, an inter-AS interconnection problem is involved.
Option C is a manner for implementing inter-AS internetworking. In the Option C manner, a BGP Label Switch Path (LSP) is first established between PE devices, and then VPN route is exchanged. By means of a multi-hop MP-EBGP, VPN routing information is directly transmitted between a source PE and a sink PE. In the Option C manner, an Autonomous System Border Router (ASBR) at an AS domain edge does not need to store VPN route, and the VPN route is processed by a PE, so that scalability is relatively good.
However, in the Option C manner, an inter-AS LSP needs to be established between PEs in different AS domains, labels are distributed within a domain by means of a Label Distribution Protocol (LDP), labels are distributed between domains by means of a single-hop External Border Gateway Protocol (EBGP), and the PEs in different AS domains transmit VPN routing information by means of a multi-hop multiprotocol (MP)-EBGP. When packet forwarding is performed, L3 label forwarding is used within a domain, and L2 label forwarding is used between ASBRs in two AS domains. Because the MPLS network needs to be deployed in both of the two AS domains communicating with each other, the OPTION C manner can implement only interconnection between homogeneous networks of an MPLS VPN.